Acute lung injury (ALI) and Acute Respiratory Distress Syndrome (ARDS) are characterized by a rapid and severe respiratory failure, arising after clinical events including major surgery, trauma, multiple transfusions and sepsis. ALI/ARDS have an associated mortality of 40-80% and current pharmacological modalities have been unsuccessful in decreasing mortality. ARDS, ALI (and other airway diseases including the Chronic Obstructive Pulmonary Disease (COPD)) are associated with neutrophil infiltration of the airway wall. Considerable observational and experimental data support a tight correlation between neutrophils and the severity and progression of the above airways diseases. The goal of the proposed research is to develop a novel class of anti-inflammatory drugs specifically targeting neutrophil functions for amelioration of lung diseases including acute lung injury/acute respiratory distress syndrome (ALI/ARDS) and chronic obstructive pulmonary disease (COPD). We propose to develop small molecule inhibitors that target Rac GTPase and Rac-p67phox interaction inhibitors to downmodulate neutrophil functions in lung diseases. The principal clinical manifestation of ARDS and ALI is edema, which results from endothelial dysfunction and microvasculature permeability. This is caused by release of free radical and reactive oxygen species (ROS) and inflammatory cytokines (e.g., TNF-1) from the activated neutrophils infiltrating the lungs. ROS production results from the activation of the neutrophil NADPH superoxide complex. The NADPH superoxide complex consists of a plasma membrane-bound flavocytochrome b558 (cyt b) and a regulatory complex, termed p47phox-p67phox-p40phox, taht is located in the cytosol of neutrophils. The p47phox-p67phox- p40phox complex translocates to the membrane in response to inflammatory signal-initiated Rac GTPase activation to produce superoxide anion (O2-) and other deleterious oxygen radicals. The direct interaction between activated Rac GTPase and p67phox is an essential step in this neutrophil inflammatory process and are the targets for our small molecule lead compounds: 1) NSC23766, a selective Rac GTPase inhibitor, and 2) phox-I, a selective p67phox inhibitor phox-I. In preliminary studies, we have established that (1) the Rac GTPases, Rac1 and Rac2, are essential regulators of neutrophil migration and superoxide production in gene targeting studies, (2) our rationally designed Rac-specific small molecule inhibitor, NSC23766, functionally suppressed Rac activity in various blood cell lineages including neutrophils, (3) our lead compound, phox-I, binds to the Rac interactive pocket of p67phox and is effective in suppressing oxidase activity in primary neutrophils, and (4) a fMLP-induced lung inflammation mouse model is useful for screening novel compounds for treating both acute and chronic lung inflammatory disorders. Thus, the present Phase I STTR proposal focuses on utilizing our detailed understanding of the molecular regulation of NOX2 NADPH oxidase by Rac GTPases to develop first-in-class treatments for acute and chronic lung disorders. It will validate the target of NSC23766 and phox-I in: A) in vitro protein-protein interaction studies, B) mouse neutrophil studies and C) human neutrophil studies (Aim1);test toxicity and pharmacokinetics in vivo and determine the efficacy of NSC23766 and phox-I in acute lung inflammation mouse model (Aim2). The long term goal is to deliver a novel pharmaceutical target, the Rac-p67phox signaling axis, and suitable lead compounds targeting this key signaling site, for the treatment of acute lung inflammatory disorders ALI/ARDS. PUBLIC HEALTH RELEVANCE: Acute lung injury (ALI) and Acute Respiratory Distress Syndrome (ARDS) are severe respiratory failure, arising after clinical events including major surgery, trauma, multiple transfusions and sepsis. In general, lung airway diseases are amongst the leading causes of morbidity and mortality in the United States of America. ALI/ARDS have an associated mortality of 40-80% and current pharmacological modalities have been unsuccessful in decreasing mortality. It is thus critically important to develop new therapies for the treatment of lung diseases. ALI and ARDS are associated with elevated neutrophil-related inflammation. The present Phase I STTR proposal will test the efficacy of two small molecule inhibitors of neutrophil functions that we have developed, on lung inflammatory disorders. Therefore, our study will help delivering a novel pharmaceutical target, and suitable lead compounds for the treatment of lung inflammation, such as ALI and ARDS.